1. Field of the Invention
The present invention relates to a positive photoresist composition that is excellent in properties as a resist (resist properties) such as sensitivity, definition, focal depth range properties (depth of focus; DOF), exposure margin, and density-dependent variations in size and is particularly useful in the formation of ultrafine resist patterns of not more than 0.35 xcexcm.
2. Description of the Related Art
Certain positive photoresist compositions containing an alkali-soluble novolak resin and a non-benzophenone naphthoquinonediazido-group-containing compound (photosensitizer) have been proposed as photoresist materials that can form ultrafine resist patterns of not more than half a micron, particularly of not more than 0.35 xcexcm, in photolithography using i-line (365 nm).
Among such photosensitizers, esters (quinonediazide esters) of a low-molecular phenolic compound having a xe2x80x9clinearxe2x80x9dphenol skeleton comprising combined four to seven benzene rings with a 1,2-naphthoquinonediazidosulfonic acid compound have been reported as photosensitizers having a high definition (e.g., Japanese Patent Laid-Open Nos. 6-167805; 7-152152; 7-159990; 7-168355; 8-129255; 8-245461; 8-339079; 9-114093; 12-29208; and 12-29209). However, a demand has been made on positive photoresist compositions that have further excellent resist properties such as sensitivity, definition, focal depth range properties (DOF), and exposure margin in the formation of ultrafine resist patterns of not more than 0.35 xcexcm, smaller than the wavelength of i-line (365 nm).
In the manufacture of logic integrated circuits (logic ICs) comprising a mixture of regular, dense patterns such as line-and-space (LandS) patterns and irregular, isolation patterns, the positive photoresist composition must form resist patterns with less xe2x80x9cdensity-dependent variations in sizexe2x80x9d, i.e., must form such dense patterns and isolation patterns in exact accordance with set dimensions with a good shape under the same exposure conditions.
In this connection, certain photolithographic techniques using short-wavelength light sources such as KrF (248 nm) and ArF (193 nm) have been proposed in the formation of resist patterns of not more than 0.35 xcexcm. However, these techniques require a significant capital investment to build plants and equipment in production lines using these light sources, and the capital investment cannot be recovered. Accordingly, the i-line (365 nm) photolithographic process, which is now mainstream, must be employed for some time in the future.
Accordingly, it is an object of the present invention to provide a positive photoresist composition that can yield ultrafine resist patterns of not more than half a micron, particularly of not more than 0.35 xcexcm, in photolithography using i-line (365 nm) and is excellent in resist properties such as sensitivity, definition, focal depth range properties (DOF), exposure margin, and density-dependent variations in size.
After intensive investigations to achieve the above objects, the present inventors have found that a positive photoresist composition including an alkali-soluble resin and a mixture of specific quinonediazide esters (photosensitizers) can yield resist patterns with satisfactory resist properties such as sensitivity, definition, focal depth range properties (DOF), exposure margin, and density-dependent variations in size even in the formation of ultrafine resist patterns of not more than 0.35 xcexcm, smaller than the wavelength of i-line (365 nm). The present invention has been accomplished based on these findings.
Specifically, the present invention provides a positive photoresist composition including (A) an alkali-soluble resin ingredient; and (B) a quinonediazide ester ingredient,
wherein the ingredient (B) includes:
(b1) a quinonediazide ester represented by following Formula (I): 
wherein each of Ds is independently a hydrogen atom or a 1,2-naphthoquinonediazido-5-sulfonyl group, where at least one of Ds is a 1,2-naphthoquinonediazido-5-sulfonyl group; and
(b2) a quinonediazide ester represented by following Formula (II): 
wherein each of Ds is independently a hydrogen atom or a 1,2-naphthoquinonediazido-5-sulfonyl group, where at least one of Ds is a 1,2-naphthoquinonediazido-5-sulfonyl group; and R1 is an alkyl group containing 1 to 6 carbon atoms.
The positive photoresist composition may further include (C) an alkali-soluble low-molecular compound having a phenolic hydroxyl group and having a molecular weight less than or equal to 1000.
The ratio of the quinonediazide ester (b2) to the quinonediazide ester (b1) in the ingredient (B) is preferably from 1% to 50% by weight.
The positive photoresist compositions of the present invention can yield ultrafine resist patterns of not more than half a micron, particularly of not more than 0.35 xcexcm, and are excellent in resist properties such as sensitivity, definition, focal depth range properties (DOF), exposure margin, and density-dependent variations in size in photolithography using i-line (365 nm).